If I Pull My Vw Heads Off Can I Put Them Right Back on Again

Cylinder Heads and Button-rod Tubes

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To go direct to your topic of involvement, encounter the following links -

• Cylinder Heads
• A Short Primer on Torque Wrench Operation
• Torquing the Cylinder Heads
• Miscellaneous Correspondence Regarding Cylinder Heads
• Push-rod Tubes
• Wisdom of Bob Hoover Regarding Push-rod Tubes

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Cylinder Heads

Note: Our feel did not include replacement of the valves and rebuilding of the heads. Bob Hoover has prepared a couple of first-class treatises on these subjects, �New Heads� and �Head Job� (unfortunately these articles are no longer available on the Internet).

Rob's 2019 note: Here's one of Bob Hoover's not bad blogs on cylinder heads...I'll let you look around the site for more. Bob Hooover on "heads"

Hither we will primarily discuss torquing of the caput nuts.

There was an editorial in a past issue of VW Trends about torquing the cylinder heads nuts. About six "experts" are quoted; half of them say that re torquing of the head nuts on a stock engine is not necessary, the others say it is. The editorial summarizes their survey with the post-obit -

The common denominator hither seems to be that, if the opportunity presents itself, it is a skillful idea to at least check the bottom, like shooting fish in a barrel-to-become-to caput nuts, and if you are running anything other than a stock 1600cc engine, then information technology should be done with more regularity. I'll get out on a limb here and propose that maybe every other valve adjustment or two, take the rocker artillery off and check the lower four. You were going to set all the valve clearances anyway, so what's four more nuts? I volition likewise recommend that if y'all are running more horsepower through a cam, headwork, bigger cylinders and pistons, or more compression, it becomes a mandatory routine. If it stops one minor problem from becoming a bigger one, it would be well worth the extra fourth dimension and endeavor.

Bob Hoover and a few others recommend retorquing the heads every time you have the engine out, just as insurance. Since there is no caput gasket to allow for whatever slack, it's more than important in a VW engine than well-nigh others. The usual result of prolonged loose head bolts is leaking combustion gases at the head/cylinder joint, which burns the heads out and ordinarily the top of the cylinder too -- bin jobs for both. In this instance, an ounce of prevention certainly IS worth a pound of cure!

New heads in the US are about $120-140 each (2006 prices), and fifty-fifty inexpensive cylinder/piston sets are well-nigh $100. As VW Trends says above, it is skilful insurance about every valve adjustment or so to check the lower 4 head nuts (the only ones you tin reach with the engine in the car).

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A Brusk Primer on Torque Wrench Operation

There are 2 common types of torque wrenches for home shop use; the "beam" type and the "clicker" type.

"Axle" Torque Wrench

"Clicker" Torque Wrench

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The "beam" blazon torque wrench is the least expensive torque wrench. Its range is typically 0-150 ft-lbs. The beam wrench works past the beam bending in response to the torque applied -- you simply utilise torque until the pointer points at the desired torque on the gauge in the handle. This type of torque wrench is very unproblematic, reliable, and accurate, and there is niggling that tin can go wrong with it when used properly. When tightening a bolt, brand sure to merely employ force in the center of the handle. This allows the beam to bend in the fashion it was designed to betoken the correct torque. Practise not over torque the wrench or the beam may curve permanently. Do not driblet the wrench because rough handling tin bend the pointer arm or pointer.

The range of a typical "clicker" torque wrench is 0-80 ft-lbs. The clicker torque wrench works by preloading a "snap" mechanism with a spring to release at a specified torque. When the mechanism releases the ratchet head it makes a "click" sound. The desired torque is set by rotating the handle until the desired torque is shown in scale in the handle (newer wrenches have a digital window that shows the desired torque). The clicker wrench is much easier to utilize because information technology is easy to set the desired torque and just pull until you experience the click. The ratchet head too makes it like shooting fish in a barrel to use in bars spaces. Information technology is good do to ready a clicker wrench to its lowest setting earlier putting it abroad to forbid the spring from taking a set. Avoid crude treatment and dropping because it can damage the mechanism. Do not use the torque wrench to loosen tight fasteners since this may damage the calibration.

Rob says - I like a "bending axle and pointer" torque wrench myself, as y'all can hold information technology at the required torque and see if the studs plough a fraction - with the clicker type, once information technology's clicked yous tin't be sure y'all are still belongings the correct torque, so you have to redo it on each stud 2-3 times to make sure. Merely if you lot have the clicker type, utilize information technology - retorquing VW heads should be done whatever time the engine is out of the car - only adept insurance. And always afterward any caput piece of work at all (valve replacement or any).

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Torquing the Cylinder Heads

Hither'southward the process for torquing the head nuts (the engine must be stone cold) -

1. If the engine is out of the car, remove the tinware around the cylinder heads. If the engine is in the car, yous volition only be able to reach the bottom 4 nuts.
2. Remove the rocker arms.
3. Brand sure you practise the head-nut tightening carefully. There are two tightening patterns: the first pattern to 7 ft-lbs, and the second pattern to the full torque of xviii or 22 ft-lbs (18 ft-lbs for 8mm studs, and 22 ft-lbs if your engine has 10mm studs).

Note: The caput bolts are quite visible with the engine out of the automobile and the tinware off, so checking the size is easy -- simply measure the bolt diameter. If you accept 8mm bolts you volition probably take "case savers" -- threaded inserts used with all 8mm head bolts to increase the thread surface area in the soft case. VW changed to the thinner bolts because they expand more than evenly with the engine as information technology heats, then the "hot" caput torque doesn't get so loftier information technology pulls the bolts out of the instance. Withal, Bob Hoover says the "hot" head torque is nigh 70 ft-lbs -- a lot more than the 18 ft-lbs cold torque! The plumbing fixtures of 14mm case savers increases the Area of thread grabbed by the head, in comparing to the thread area of the 10mm studs which were screwed directly into the case material. So the by trouble of studs working loose in the case is almost completely eliminated. The 14mm example savers use the 8mm studs.

4. First the vii ft-lb sequence: torque each of the eight nuts to 7 ft-lbs in the sequence shown below -

   As you are looking at the cylinder head with the valve encompass removed -

   top of engine

   7 5 6 viii
   3 i ii iv

5. Then torque the nuts once more again to 18 ft-lbs for the 8mm studs and 22-23 ft-lbs for the 10mm studs, in the sequence shown -

   Exercise Non exceed the figures above - they are designed to provide the required 70 ft-lbs of torque needed to seal the heads to the cylinders in one case the engine heats up.

   top of engine

   viii 2 4 6
   5 1 3 7

6. If you over-torque a nut, loosen them all (to non less than seven ft-lbs) and redo them in sequence.

Dave institute that all of the head bolts in his '71 1600cc dual-port engine are 10mm, so 22-23 ft-lbs is the correct torque. In his offset experience with the caput basics he found that they were all loose -- something like 18 ft lbs. There were little screws/bolts missing EVERYWHERE in the engine can!

Rob wrote - Maybe your ham-fisted mechanic just knew the 18 ft-lb figure, and uses information technology on all Bugs! Isn't it amazing how well our Bugs they can run with bits missing. Only it feels really good to get it all buttoned up right doesn't information technology!

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Miscellaneous Correspondence
Regarding the Cylinder Heads

Someone wrote - The engine was pinging like crazy, and it felt like it was running on three cylinders. I took it to a VW specialist; they institute the timing to be at 26 degrees advanced and said the head gasket was blown.

Rob responded - The VW engine does not employ a caput gasket. The cylinders sit inside a recess cut into the cylinder caput (this is chosen fly cutting the head) and a seal is made between the recess in the caput and the summit rim of the cylinder itself. If this area becomes damaged or overheated in any manner, loftier temperature combustion gases leak out, causing called-for of the head and cylinder top, requiring expensive repairs. The "running on three cylinders" you describe is typical of an engine with at least one damaged cylinder/head articulation (assuming all cylinders have working spark plugs and the correct fuel/air mixture is beingness supplied).

Even when setting upwards an engine for reduced compression (to run on VERY low octane fuel), spacers are usually placed betwixt the cylinders and case, not betwixt cylinders and heads. I'thousand not sure what your "vw Specialist" was suggesting re head gaskets. But finding the timing advancved to 26 degrees (presumably you mean at idle, non max advance) was a proficient find. Idle advance is usually around 7.5BTDC and max advance is normaly effectually 30 degrees (009 distributors) or up to 40 degrees (vacuum distributors).

Another guy wrote - After torquing down the heads on my '67 Problems (cylinders are new and the heads new/rebuilt) I noticed something that didn't look right. The heads didn't seat all the manner -- I could notwithstanding come across space between the heads and the cylinders.

Rob responded - Eh??? The heads are fly cutting (recess for the heads to fit in), I don't understand how you could meet a space between head and cylinder inside that recess. Unless you habe a mismatch between the heads and cylinders.

Since there is no head gasket on VW engine, the mating between the heads and the cylinders is vital -- information technology's what seals the combustion bedroom. Any leaks at that place, even tiny ones, will result in burned cylinder tops and/or burned heads around the sealing lip. Then don't try to first the engine until you are certain the heads are correctly seated.

The but manner the head could be "cocked" so only one cylinder wasn't sealing properly is if the cylinder is not seated in the instance correctly (resulting in ane cylinder beingness high), or the head is damaged.

Before the heads go on, you should be able to place a directly edge across the cylinder tops and see information technology impact the two cylinder rims in four places -- then yous know the cylinders are fully seated in the case and are identical heights.

The guy wrote over again - I pulled the heads and cylinders to encounter what was going on. The cylinders practice indeed sit flush on that lip in the heads, although in that location is slight motion (I can wiggle the cylinder back and forth e'er so slightly). The gap that I was referring to, (and the part that has me dislocated), is between the flat part of the head and lip on the cylinder. One of the cylinders sits affluent on the raised 1/two moon portion of the head. But the other 3 don't quite affect the moon - they are all unlike sizes, the largest creating a gap .082 (measured from cylinder lip to apartment function on caput, in between moons).

Rob responded - The slight movement of the cylinder is normal. The fly-cutting in the heads is fractionally larger than the cylinder rim, so there is room for the cylinder to move just a fraction within the caput. But I still don't understand "flat part of head" -- do you mean the underside of the bottom fin (nearest the case) or are you talking virtually the inside of the fly cutting recess?

The altitude between the outermost cylinder fin and the innermost head fin might vary a little - the critical measurement is the length of the cylinder between the case and the outer rim. The case needs a completely flat area where the cylinders slot into the instance, so, with even height cylinders the outer rims of next cylinders will be a perfectly directly line. The recesses (wing-cut) in the heads are cut to an verbal depth too, so when the heads go on both cylinder rims will sit straight inside their recess and seal properly when the head studs are torqued.

It'southward a complicated part of the VW engine blueprint, an unusual design to have twined heads just separate cylinders (horizontally opposed aircraft engines use separate heads for each cylinder for instance). That makes it essential that both cylinders sit at exactly the aforementioned height, or the head won't seal properly on both cylinders.

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Push-rod Tubes

Please see our Push-rod Tube Process.

Rob explained how the push-rod tubes work -

The VW engine has four separate cylinders and and two cylinder heads, and therefore does not have internal openings for the push-rods to sit in, equally happens in an "inline" watercooled engine with a full engine block. Therefore the push button-rods have to take tubes around them. These tubes provide the return path for the oil flowing back from the valves to the sump, and even provide some cooling for the returning oil which has been heated by contact with the very hot heads, and then flowing past the cooling airstream for the cooler running cylinders. A very clever slice of engineering by Mr. Porsche.

The tricky bit is that since metal expands when information technology gets hot, the VW engine grows and tiny bit wider each time it runs (and a fraction longer too, merely the engine example is not the problem here). So the button-rod tubes have to exist able to expand and contract a mm or two, and at the same fourth dimension must seal against both the heads and the case to provide a airtight oil path back to the sump. This is why they have a concertina department at each terminate -- to provide the "spring" needed to seal the neoprene washers at each stop (to the head and instance), and to allow for the engine expansion with oestrus.

BUT -- the neoprene washers do gradually harden with historic period (takes a long time), and the concertina sections do loose a little of at that place "bound". So leaks can develop here. And damage/bends to the tubes can brand this worse. And they can rust from the outside, resulting in pivot-holes.

To cheque for leaks, get under the auto after it has been on a run, and look very closely at the push-rod tubes themselves just under each cylinder. If they await fresh moisture with oil, or there is a mess of oily deposits on the cooling tinware under the push-rods, this may exist (partly at to the lowest degree) your problem. Be conscientious -- don't burn down your olfactory organ on the hot exhaust/engine when doing this!!!

If leaky/damaged push-rod tubes were your only problem, there is a replacement tube which can be fitted without removing the engine I oasis't always used these so I can't draw the process exactly, except to say that the pushrods must be removed, the new tubes installed and elongated to seal at each finish, so the push rods reinstalled and the valve clearances reset. Only since you may have to install new cylinders/pistons anyhow, the original equipment type of tubes can be used. The one-time tubes will exist fine if they are not damaged/rusted (and they must be straight), but you MUST supplant all the neoprene washers (two for each tube). The "sometime boys" trick is to gently stretch the tubes a lilliputian (measure the length of each tube, and then pull outwards gently on the concertina sections till information technology'southward a few mm longer, but don't overdo it) before reinstalling. This provides renewed "leap" to the tubes and ensures a good seal on the new washers.

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The Wisdom of Bob Hoover

Bob Hoover has written an interesting �sermon� on push-rod tubes (unfortunately Bob'southward famous sermons are no longer available on the Internet). Only a note or two from the article -

The button-rod tubes grade an oil-tight conduit between the valve gallery and the crankcase, assuasive multiple return paths for the oil pumped out to the rockers through the push-rods. At overhaul time information technology's best to use new push button-rod tubes since the bellows portion on either makes them specially difficult to clean. They cost well-nigh a buck each, cheap insurance

The stock tubes are wizards at getting rid of heat! Given a sparse coat of flat black paint to preserve them and lower their thermal resistance, your eight push-rod tubes serve as eight auxiliary oil coolers

Since the push button-rod tubes are bathed in the flow of air that has only passed over the cylinders, the air is hot. But not as hot as the oil coming from the valve gallery. The cylinder caput is the second-hottest part of your engine (the exhaust valves and stacks are first) and the oil in the valve galleries is typically a hundred degrees or more above the oil temperature in the sump. But that brusque trip down the button-rod tubes is sufficient to suck a lot of the heat away, thanks to the slightly cooler air coming off the cylinders and the generous surface expanse of the push-rod tubes.

If y'all supplant your stock button-rod tubes with those trick ii-function anodized aluminum jobbies so beloved of show-auto freaks, you've just thrown away ane of the more subtle gems of the VW engine design.

Whatever you practice, don't fifty-fifty call back of using two-part push-rod tubes. They will brand your engine run hot.

- Bob Hoover (used with permission)

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Rob discussed the ii-role push-rod tubes - The ii-part push-rod tubes were manifestly designed and then you remove the rocker arm, pull out the push-rod, yank out the one-time tubes sideways (probably where virtually of the gross damage occurred as they are supposed to be removed afterward the heads are off, put the long section of new tube in place, then shrink the leap section on the brusque piece so it tin be inserted and the spring and thin seal seals the two pieces together, while pushing the whole assembly in both directions to seal the ends against caput and case. And so put the push button-rods dorsum in and replace the rocker arm.

Someone wrote - The mechanic who will be removing my engine said that carbon builds upward in the heads, and if I pull out the push button-rod tubes the carbon will fall away, so that "natural" seal will disappear and my engine will start passing oil, or burning it.

Rob responded - With respect, you need a different mechanic! The combustion seal is really the top of the cylinder against the recessed "fly cut" in the cylinder head. Provided the heads and cylinders are accurately cut, and the head studs are torqued correctly, this makes a good seal. This has NOTHING to do with the pushrod tubes and their seals. They come into contact with hot lubricating oil which flows from the rocker cover area back to the sump, and never see any of the combustion gases.

If you are worried almost it, you can get push-rod tubes that don't need the heads off to replace - they telescope into position. But in that location are at least 2 sorts of these, and at least one sort leaks badly (I've never had to use them myself). Ask John at Aircooled.Cyberspace about the best ones -- if you decide to used them. Note that Bob Hoover above says that the shiny two-part replacement pushrod tubes don't cool the oil passing through them most as much as the stock tubes do. If you lot want to apply the original type, yous just stretch the former tubes a few mm and use new end-seals, and place the seams at the top when re-assembling. The original concertina tubes can only exist replaced or stretched with the heads removed.

You lot must install new cease-seals when you replace the push button-rod tubes, and you MUST stretch the tubes a trivial before you put them back in, then that they button the new seals into the head and case firmly so as to brand a good seal. The tapered side of the seal must point to the heads and case at each end. Measure each one and stretch them just a few mm. If you lot do it as well much they might cleft. And brand certain that the weld is pointed upwards - just in case information technology ever starts to leak (unlikely, but....)

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Source: http://www.vw-resource.com/heads.html

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